Method and apparatus for producing underwater oil fields



J. A. HAEBER Dec. 20, 1966 METHOD AND APPARATUS FOR PRODUCING UNDERWATEROIL FIELDS 4 Sheets-Sheet 1 Original Filed Sept. 12, 1963 INVENTOR JOHNA. HAEBER n flai ims AGENT J. A. HAEBER Dec. 20, 1966 METHOD ANDAPPARATUS FOR PRODUCING UNDERWATER OIL FIELDS 4 Shets-Sheet 2 OriginalFiled Sept. 12, 1965 FIG. 3

FIG. 9

lNVENTOR JOHN A. HAEBER 8Y HIS AGENT FIG. 2

Dec. 20, 1966 J. A. HAEBER 3,292,695

METHOD AND APPARATUS FOR PRODUCING UNDERWATER OIL FIELDS Original FiledSept. 12, 1963 4 Sheets-Sheet 5 INVENTOR JOHN A.HAEBER BY- FIG. 4

HIS AGENT Dec. 20, 1966 J. A. HAEBER 3,292,695

METHOD AND APPARATUS FOR PRODUCING UNDERWATER OIL FIELDS Original FiledSept. 12,1965 4 Sheets-Sheet 4 INVENTOR JOHN A. HAEBER 9 HIS AGENTUnited States Patent f 3,292 695 METHOD AND APPARATUS FOR PRODUCINGUNDERWATER OIL FIELDS John A. Haeber, Houston, Tex., assignor to ShellOil Company, New York, N.Y., a corporation of Delaware Originalapplication Sept. 12, 1963, Ser. No. 308,531. Divided and thisapplication July 21, 1965, Ser. No.

2 Claims. c1. 166.5)

The present application is a divisional application of copendingapplication Serial No. 308,531, filed September 12, 1963.

This invention is directed to methods and apparatus for producingunderwater oil and gas fields wherein the wellhead assembly mounted onthe top of each Well is positioned at a substantial distance below thesurface of a body of water and is preferably positioned on the oceanfloor.

A recent development in the oil industry is the development of oiland/or gas fields which are located underwater and oftentimes at asubstantial distance, say to 100 miles olfshore. Since well structureswhich extend to a point about the surface of the water form navigationhazards for ships operating in the vicinity, a new development has beenthe placement of the wellhead assemblies on the ocean floor. Wells ofthis type are presently produced by running the production flow linesfrom the well to shore or to a stationary production facility mounted onpiles at an offshore location. The use of flow lines running to shorelimits the production of wells located many miles from shore as theoil-producing formation which is traversed by the well must be undersubstantial pressure so as to provide sufiicient pressure to producetheoil and other well fluid up the well and then to overcome the frictionalresistance encountered in the many miles of flow line extending toshore. On the other hand, the use of stationary production platforms islimited to rather shallow water depths as it is very costly to installsuch platforms in deep water and the cost would be prohibitive toconstruct and install stationary platforms for oil field purposes indeep water say over 400 feet in depth.

It is therefore a primary object of the present invention to provideapparatus and methods for producing underwater oil fields wherein thewellhead assemblies are positioned on the ocean floor in water of anydepth.

A further object of the present invention is to provide methods andapparatus for reducing or minimizing, the wells tubing pressure(pressure in the production tubing at the wellhead) and thereby (l)prolong the wells period of nautral flow (if any), (2) increase theproduction rate of the well and (3) reduce the amount of lift gasrequired to produce the well after natural flow has either ceased ordeclined to where the use of lift gas is beneficial.

Another object of the present invention is to provide methods andapparatus for supporting flow lines and other field collecting anddistribution lines extending from the ocean floor to a position near thesurface of a body of water.

A still further object of the present invention is to provide apparatusfor supporting vertically-extending well flow lines and other fieldcollecting and distributing lines above the ocean floor while providingmeans for connecting the flow lines to a suitable vessel at the surfacefor receiving the production fluid from the wells.

Still another object of the present invention is to provide apparatusfor handling a multiphase production fluid from an underwater oil fieldwhereby the gaseous phase of the production fluid may be separated fromthe oil phase before the oil phase is raised above the ocean floor.

ice

Still another object of the present invention is to provide a method andapparatus for separating a multiphase oil production fluid in a vesselat the surface of the ocean and returning the oil phase of theproduction fluid down to storage facilities positioned on the oceanfloor.

These and other objects of this invention will be understood from thefollowing description when taken with reference to the drawing, wherein:

FIGURE 1 is a synoptic view illustrating an underwater oil field havinga plurality of wells drilled therein and connected to a productionfacility on the ocean floor which in turn is connected in fluidtightcommunication with a verticallyextending cylindrical structurepositioned in the ocean floor and extending upwardly to a point near theocean surface where it is connected with a floating vessel or productionfacility on the surface, the production facility on the surface alsobeing in communication with suitable storage tanks located on the oceanfloor;

FIGURE 2 is a longitudinal view diagrammatically illustrating thevertically-extending elongated cylindrical structure which extends intothe ocean floor and is anchored therein;

FIGURE 3 is an enlarged cross-sectional view taken along the line 33 ofFIGURE 2;

FIGURE 4 is an enlarged longitudinal view, taken partially incross-section, illustrating a pump mechanism carried within the verticalcylindrical structure of FIG- URE 2;

FIGURES 5 and '6 are fragmental views, taken partially in cross-section,illustrating one method of connecting underwater piplelines to thevertical cylindrical structure of FIGURE 2;

FIGURE 7 is a cross-sectional view taken along the line 7-7 of FIGURE 4;

FIGURE 8 is a cross-sectional view taken along the line 8-8 of FIGURE 7;and,

FIGURE 9 is a fragmental view taken in the longitudinal cross-section ofone form of a means for connecting pumping apparatus to the top of thevertical cylindrical structure of FIGURE 2.

Referring to FIGURE 1 of the drawing, a plurality of underwater wellsare illustrated with their wellhead assemblies 11, 11a and 11bpositioned on the ocean floor 12. Each production wellhead assembly, forexample wellhead assembly 11 is provided with a least one flow line 13and preferably two flow lines 13 and 14 whereby the well productionfluid may be taken away through one line, and if necessary, gas may bepumped down through the other line during later well life in order toproduce the well. The other Wellhead assemblies 11a and 11b are alsoprovided with dual flow lines 13a, 14a and 13b, 14b, respectively.

The production flow lines from the various underwater Wells preferablylead to a production facility, generally represented by numeral 15,which is located on the ocean floor and is normally centrally locatedamong the wells which are connected to it. The production facility 15may be of various types. For example, the production facility 15 may bemerely a manifolding station where the production fluids from theseveral wells are combined so that they can be delivered by a singleflow line to a distant terminal. On the other hand, the productionfacility 15 may also be provided with suitable metering devices formetering the individual flow from each of the wells prior to combiningthe several flows and sending them to the distant terminal.

As most oil is combined with gas in many oil fields, the productionfacility 15 is preferably provided with suitable separators 16 forseparating the gas from the oil before flowing the oil to the distantterminal. While high pressure gas separators 16 may be employed early inthe life of the well, the production facility is also preferablyprovided with low pressure gas separators 17 for use during the latterpart of the well life. The production facility 15 may have a base frame18 secured to the ocean floor and equipped with guide columns 19 onwhich a central removable frame 20 is positioned. The variousmanifolding lines and separators 16 and 17 are secured to and areremovable with the inner rfame 20 which is also preferably provided witha track 21. The track is employed in order to facilitate ease ofpositioning an underwater manipulator device adapted to open and closevalves or to connect or disconnect various flow lines one from theother. Each of the flow lines coming to the production facility 15 isprovided with a remotely-actuatable pipe connector 22 of any type wellknown to the art so that the flow lines may be disconnected from theproduction facility 15 before the central removable frame 20 and itsassociated equipment are pulled back to the surface for maintenance orrepairs.

The flowlines coming from the production facility 15 may be boundtogether in the form of a single bundle of lines 24, as illustrated inFIGURE 1. If the production facility 15 is merely a manifolding station,only a single flowline 24 would be needed during the early life of thewells. However, if the wells were produced by gas lift during the latterpart of their life, the bundle of lines 24 should at least consist of aproduction flowline away from the production facility 15 and a gas lineextending to the production facility 15 and thence on to the individualwells 11, 11a, and 1117. In the event that the production facility 15also includes gas separation apparatus, the bundle of lines 24 shouldpreferably include separate gas lines for high and low pressures to andfrom the high and low pressure gas separators 16 and 17, respectively.

.Additional lines may connect the production facility 15 with a distantterminal so that various types of well maintenance tools or instrumentscan be pumped down to the production facility 15 or to any of theindividual wells for carrying out certain selected operations. It is tobe understood that in an oil field having a great number of wells aplurality of production facilities 15 would be Lsunken and anchored tothe ocean floor. The upper end of the elongated tubular or cylindricalstructure is located I below the surface 26 of the ocean so as to berelatively unaffected by wind and Wave forces and so that it does notconstitute a hazard to navigation of ships in the area. For example, inwaters 1000 feet deep the vertical cylinder may have 900 feet extendingabove the ocean floor 12, while several hundred feet are sunk in theocean floor to anchor it securely in a vertical position. The verticalcylindrical structure may be in the order of 6 feet in diameter in itspreferred form and as much as 2 inches in wall thickness to give itsubstantial rigidity. The vertical cylinder 25 may be originallytransported to its offshore location on a series of barges or the endsof the cylinder 25 may be closed so as to aid in floating the structureto its desired location. The lower end of the vertical cylinder 25 maybe jetted into the ocean floor in a manner well known to the art or itmay be provided with a large diameter bit or series of bits mounted on arotatable housing of the type well known to the art for drillinglargecylinder and the ocean floor formations so as to cement thevertical cylinder or free-head pile 25 in place in a flowlines extendingfrom the ocean floor 12 to the floating production facility generallyrepresented by numeral 30 (FIG. 1) which floats on the surface of theocean 26. By

using the vertical cylindrical support structure 25 of the presentinvention, a smaller floating production facility or a floatingproduction facility with less buoyancy can be employed as the floatingproduction vessel 30 only supports the flowlines between the vessels 30and the top of the vertical cylinder 25 rather than having to supportthe thousands of feet of steel flowline extending from such a productionvessel 30 to the various Wells or production facilities on the oceanfloor when the production vessel 30 is positioned in, say, 1000 feet ofwater. In the event that flexible flowlines are used, a greater numberof support plates 27 would be employed as needed to prevent the flexibleflowline from pulling apart under its own weight.

It is apparent that with floating production units, some motion of theplatform is certain to occur regardless of how sophisticated a mooringsystem is used. This motion will chafe and deteriorate the lines hangingfrom the facility, and the loss hazard will be particularly high duringstormy periods. If the lines are hanging free from the productionfacility deck, the lines are likely to part at or nearthe sea floor whenfailure takes place.. However, when the lines are supported throughout alarge portion of the sea floor to production facility deck interval ofthe present invention, with flexible pipe being used only for the freehanging portion between the top of the free-head pile and the productionfacility, the locus of failure is concentrated near the sea surface.Replacement of parted and damaged lines in this interval can beaccomplished with relative ease and speed and at much less cost than ifthe failure had occurred at or near the sea floor. Thus, although use offloating production platforms probably necessitates accepting higherfailure rates of flow lines and collecting and distribution lines, theeconomic consequences of these failures can be at least partiallycontrolled by controlling the location of the failures by employing theapparatus of the present invention.

The floating production facility 30 may be a vessel of any suitable formwhich is maintained substantially directly over the elongated verticalcylinder 25 in any manner well known to the art. Thus, the productionvessel 30 may be flexibly anchored in place by a series of anchors andanchor lines (not shown) or the vessel may be pro- .vided with a seriesof propulsion units adapted to move the vessel in any'direction so as tomaintain it substantially over the vertical cylinder 25. One form of aproduction vessel may be triangular, as shown, with the hull made up ofbuoyancy cylinders 31, 32, and 33 at the. corners while theinterconnecting cross bracing members 34 are preferably hollow and formstorage tanks for the oil produced from the wells until such time theoil is delivered to a tanker or barge 35. In the event that gas is notseparated from the production fluid at the ocean floor productionfacility 15 (FIGURE 1), the floating production vessel 30 is providedwith suitable separating apparatus for separating gas and/ or water fromthe oil produced. In addition to separators, the floating productionvessel may be provided with heater-treaters or other demulsifyingapparatus, metering tanks, etc. Although only two flowlines 37 and 38are shown in FIGURE 1 as extending between the top of the verticalcylinder 25 and the production vessel 30, it is to be understood thatthese may be bundles of flowlines or other flowlines may extendindividually between the vessel and the vertical cylinder 25. Inaddition, power lines 39 extend from the production vessel 30 tosuitable pumping apparatus whose power units are located at the top ofthe vertical cylinder 25, as will be described hereinbelow.

As illustrated in FIGURE 1, the apparatus of the present invention mayalso include a series of interconnected storage tanks 40 to 45preferably positioned in a frame 46 which in turn is anchored to theocean floor 12. A fiowline 47 extends from the interconnected tanks 40to 45 and includes an oil conduit extending up the vertical cylinder 25and to the production vessel 30. Thus, the ocean floor storage tanks 40to 45 may serve as auxiliary storage capacity for the production vessel30 in'the event that the tanker 35 is delayed due to storms, etc. Anysurplus oil that cannot be held in the storage tanks in thecross-members 34 of the production vessel 30 may be pumped down flowline47 alongside the vertical cylinder 25 and into any of the tanks 40 to45. The oil could be returned to the vessel in any suitable manner as bymeans of sea-water displacement. The lowest point on the tanks is leftopen to the sea water to bleed off b. s. and w. (basic solids and water)and to equalize internal and external tank pressures to avoid burstingor collapsing the tanks. Therefore, it is necessary to pump crude oilinto the tanks with a pressure equivalent to the difference between thesea water head and the crude oil head. For unloading the tanks, it isnecessarly only to open a valve on the crude line at the surface topermit the sea water head to displace crude from the tanks. Ifwithdrawal rates higher than those obtainable by sea water displacementare required, the flow rate can be increased by pumping or gasliftingthe crude. For emergency purposes, it may be desirable in some cases toarrange the flowlines and manifold in a manner such that the wellproduction fluid passing through the flowline bundle 24 can flowdirectly into the storage tanks 40 to 45 in the event of power failureson the production vessel 30. This could be done rather than shut in thewells.

As shown in FIGURE 2, a pump motor housing 50 is illustrated as beingpositioned on the top of the vertical cylinder 25 and secured thereto asby means of any suitable connector 51. The pump housing is shown ingreater detail in FIGURES 4 and 7 as enclosing one or more pump motors,in this case three pump motors 52, 53 and 54 with the discharge lines 55and 56 from the smaller pumps 52 and 53 being connected to the maindischarge line 57 from the large pump 54 so that only one productionfluid line 57a extends between the pump housing 50 and the productionvessel 30. The discharge lines 55, 56, and 57 may be provided with checkvalves 58 59 and 60. A plate 61 closes the bottom of the pump housing 50and maintains it separated in a fiuidtight manner from the interior ofthe vertical cylinder 25. As shown in FIGURE 4 a discharge pipe 62extends through the plate 61 and out through the wall of the pumphousing 50 through a flexible line to the production vessel 30 so as todischarge any gases accumulating at the top of the vertical pile orcylinder 25 below the plate 61. The electrical leads 39 may enter thepump lhousing 50 through the same wall as the pipe 57a (FIGURE 7). Thepump motors 52, 53 and 54 are arranged to drive shafts or rods 63, 64and 65, respectively, of suitable centrifugal or deep well pumps 66, 67and 68, respectively. Preferably, the capacities of the pumps areselected so that the large pump will run all the time and one or more ofthe small pumps will he run in an on-and-olf manner so that theproduction fluid in the vertical cylinder 25 is maintained at thedesired level. Preferably, the liquid level in the vertical cylinder 25is maintained near the lower end thereof close to the inlet for theproduction fluid so that there is little hydrostatic head being appliedto the low pressure-gas-oil separators at the production facility(FIGURE 1). Hence, with or without employing the ocean-floor productionfacility 15 between the Wellhead 11 and vertical cylinder 25, bymaintaining the level of production fluid low in the vertical cylinder25 the wells would have less of a hydrostatic head against which toproduce. Thus, it may be seen that by employing the vertical cylinder 25of the present invention as a receiver having little or no hydrostatichead applied thereto, that low pressure wells could be produced, or oldwells could be produced for a longer part of their life, beforeresorting to gas lift methods.

Any suitable type of liquid-level controller may be employed to controlthe liquid level within the vertical cylinder 25. In one commercial forma liquid-level controller an open-ended pipe is immersed in the liquidbody and air is pumped through. As the hydrostatic head builds up aroundthe pipe and it is harder to discharge the air from the pipe, a sensingdevice on the vessel will indicate this change in liquid level and startone of the pumps which runs until the liquid level has been againreduced to the desired point. In FIGURE 4, the vertical cylinder 25 isshown as having a 2 inch line 69 extending down to a predetermined levelabove the uppermost pump 68. This pipe 69 would be in communication withthe vessel through a flexible line 70 (FIGURE 2). The pumps 66, 67 and68 are suspended from shaft housings 71, 72 and 73 which surround theshafts 63, 64 and 65, respectively.

The pump housing 50 is removably secured to the top of the verticalcylinder 25 so that maintenance work can be done on the pumps asrequired. Although bolts could be unbolted by a suitable underwatermanipulator as will be described hereinbelow, the housing may beprovided instead with a suitable hydraulic or mechanical connector. Oneform of a suitable connector is shown in FIGURE 9 wherein the innersurface of the vertical cylinder 25 is provided with annular grooves 74therein adapted to receive outwardly-extendible latching dogs 75 carriedby a downwardly-extending Wall 76 of the pump housing 50. The wall 76has formed therein an annular chamber in which an annular piston 78 isslidably mounted for a limited vertical movement. Hydraulic pressure canbe supplied through conduits 79 or 80 to the top or bottom of the piston72 to either lock or unlock the latching dogs 75 from the groove 74.Thus, when it was desired to remove the pump housing and pumps from thevertical cylinder 25, the latching dogs 75 of the connector 51 would beretracted and the whole housing and pumps would be pulled back to theproduction vessel by any suitable hoisting means.

Arranged near the bottom of the vertical cylinder 25 just above theocean floor 12 (FIGURE 5) are one or more fluid inlet ports 82 throughwhich production fluid is delivered to the vertical cylinder 25 from aproduction line 24a which in turn is connected to the ocean floorproduction facility 15 (FIGURE 1) or directly to one of the wells. Thepipe 24a may be originally connected to the vertical cylinder 25 bylowering it by means of a line 83 into a V-grooved or U-shaped openingat the top of an aligning and support bracket 85 secured to the outersurface of the vertical cylinder 25. A coupling 86 having anoutwardly-extendible telescoping sleeve 87 is provided at the fluidinlet 82 in order to connect to the free end of the production line 24ain a fluidtight manner. The sleeve 87 may be moved outwardly in anysuitable manner as by means of turning the actuating nut 88. For thispurpose an underwater manipulator may be employed which is eithersuspended from a track 90 secured to the outside of the verticalcylinder 25, or may be of the type that rests on the ocean floor whilecarrying out operations. An underwater manipulator of this type isdescribed in US. Patent 3,099,316 and includes a body member 91 providedwith wheels 92 for propelling it around the track 90, propulsion units93 for moving it through the water, a support and/or power cable 94, aunit 95 containing lights and a television camera, as well 7 as anextendible arm 96 having a wrench head 97 at the end thereof formanipulating various elements such as actuating bolt 88 on the connector86.

' In FIGURE 6 the underwater manipulator device described with regard toFIGURE is shown as being employed to connect another form of coupling 98by turning its actuating screw 99 so as to connect lines 28 and 24btogether in a fluidtight manner.

It may be seen from the above description that a method has beenprovided for producing deep water oil and gas field in which a pluralityof wells have been drilled. The method includes the steps of installinga large-diameter vertical cylinder on the ocean floor with the upper endbelow the surface of the ocean, producing well fluids from the wellsinto the lower portion of the cylinder, providing a vessel on thesurface of the ocean in the vicinity of the cylinder, connecting theinterior of the cylinder in fluid communication with the vessel, andsubsequently pumping well fluid from the cylinder to the vessel,preferably maintaining the level of the fluid in the cylinder in thelower portion thereof so as to reduce any hydrostatic head in thecylinder which would reduce the ability of the wells to produce undertheir own pressure. In addition, when the well production 'fluidcontains gas the present method is altered to include the operation ofseparating the gas from the well fluid before the fluid enters thevertical cylinder. Alternatively, the method of the present inventionincludes the operation of separating a multiphase production fluid intoits various components at the vessel on the surface of the ocean, and inthe event that the storage capacity of the vessel is not suflicient,production fluid in the form of oil may be pumped back down to storagefacilities on the ocean floor.

I claim as my invention:

1. A method of producing an underwater oil' and gas field in which aplurality of wells have been drilled, said method comprising the stepsof:

installing a large diameter vertical cylinder in the ocean floor andpartially buoyantly supporting the upper end of said vertical cylinderbelow the surface of the ocean, producing well fluid from said wellsinto a lower portion of said cylinder,

providing a vessel on the surface of the ocean in the vicinity of thecylinder,

connecting the interior of the cylinder in fluid communication with thevessel, and

pumping well fluid from said lower portion of cylinder to said vessel.

2. The method of claim 1 wherein the level of well fluid in saidvertical cylinder is maintained in the lower portion of said cylinder toreduce the hydrostatic head normally acting against the fluid beingproduced from an underwater well.

References Cited by the Examiner UNITED STATES PATENTS 2,594,105 4/ 1952Watts 1140.5 2,731,168 1/ 1956 Watts 1140.5 2,783,970 3/ 1957 Gillespie166-0.5 2,990,796 7/ 1961 Cole et al. 6146.5 3,063,507 11/1962 ONeill etal 1660.5 3,111,692 11/1963 Cox 1660.5

CHARLES E. OCONNELL, Primary Examiner. R. E. FAVREAU, AssistantExaminer.

1. A METHOD OF PRODUCING AN UNDERWATER OIL AND GAS FIELD IN WHICH APLURALITY OF WELLS HAVE BEEN DRILLED, SAID METHOD COMPRISING THE STEPSOF; INSTALLING A LARGE DIAMETER VERTICAL CYLINDER IN THE OCEAN FLOOR ANDPARTIALLY BUOYANTLY SUPPORTING THE UPPER END OF SAID VERTICAL CYLINDERBELOW THE SURFACE OF THE OCEAN, PRODUCING WELL FLUID FROM SAID WELLSINTO A LOWER PORTION OF SAID CYLINDER,